Hi,
The header of patch #0 is broken for the patch set. However, it seems
BPF CI still can handle it and the content of patch #0 is still intact,
so I will not resend the patch set and instead I will respin it after
receiving some comments. Sorry for the inconvenience.
On 1/6/2025 4:18 PM, Hou Tao wrote:
> Hi,
>
> The use of migrate_{disable|enable} pair in BPF is mainly due to the
> introduction of bpf memory allocator and the use of per-CPU data struct
> in its internal implementation. The caller needs to disable migration
> before invoking the alloc or free APIs of bpf memory allocator, and
> enable migration after the invocation.
>
> The main users of bpf memory allocator are various kind of bpf maps in
> which the map values or the special fields in the map values are
> allocated by using bpf memory allocator.
>
> At present, the running context for bpf program has already disabled
> migration explictly or implictly, therefore, when these maps are
> manipulated in bpf program, it is OK to not invoke migrate_disable()
> and migrate_enable() pair. Howevers, it is not always the case when
> these maps are manipulated through bpf syscall, therefore many
> migrate_{disable|enable} pairs are added when the map can either be
> manipulated by BPF program or BPF syscall.
>
> The initial idea of reducing the use of migrate_{disable|enable} comes
> from Alexei [1]. I turned it into a patch set that archives the goals
> through the following three methods:
>
> 1. remove unnecessary migrate_{disable|enable} pair
> when the BPF syscall path also disables migration, it is OK to remove
> the pair. Patch #1~#3 fall into this category, while patch #4~#5 are
> partially included.
>
> 2. move the migrate_{disable|enable} pair from inner callee to outer
> caller
> Instead of invoking migrate_disable() in the inner callee, invoking
> migrate_disable() in the outer caller to simplify reasoning about when
> migrate_disable() is needed. Patch #4~#5 and patch #6~#19 belongs to
> this category.
>
> 3. add cant_migrate() check in the inner callee
> Add cant_migrate() check in the inner callee to ensure the guarantee
> that migration is disabled is not broken. Patch #1~#5, #13, #16~#19 also
> belong to this category.
>
> Considering the bpf-next CI is broken, the patch set is verified by
> using bpf tree. Please check the individual patches for more details.
> Comments are always welcome.
>
> [1]: https://lore.kernel.org/bpf/CAADnVQKZ3=F0L7_R_pYqu7ePzpXRwQEN8tCzmFoxjdJHamMOUQ@xxxxxxxxxxxxxx
>
> Hou Tao (19):
> bpf: Remove migrate_{disable|enable} from LPM trie
> bpf: Remove migrate_{disable|enable} in ->map_for_each_callback
> bpf: Remove migrate_{disable|enable} in htab_elem_free
> bpf: Remove migrate_{disable|enable} from bpf_cgrp_storage_lock
> helpers
> bpf: Remove migrate_{disable|enable} from bpf_task_storage_lock
> helpers
> bpf: Disable migration when destroying inode storage
> bpf: Disable migration when destroying sock storage
> bpf: Disable migration when cloning sock storage
> bpf: Disable migration in bpf_selem_free_rcu
> bpf: Disable migration in array_map_free()
> bpf: Disable migration in htab_map_free()
> bpf: Disable migration for bpf_selem_unlink in
> bpf_local_storage_map_free()
> bpf: Remove migrate_{disable|enable} in bpf_obj_free_fields()
> bpf: Remove migrate_{disable,enable} in bpf_cpumask_release()
> bpf: Disable migration before calling ops->map_free()
> bpf: Remove migrate_{disable|enable} from bpf_selem_alloc()
> bpf: Remove migrate_{disable|enable} from bpf_local_storage_alloc()
> bpf: Remove migrate_{disable|enable} from bpf_local_storage_free()
> bpf: Remove migrate_{disable|enable} from bpf_selem_free()
>
> kernel/bpf/arraymap.c | 6 ++----
> kernel/bpf/bpf_cgrp_storage.c | 15 +++++++-------
> kernel/bpf/bpf_inode_storage.c | 9 ++++----
> kernel/bpf/bpf_local_storage.c | 38 +++++++++++++++-------------------
> kernel/bpf/bpf_task_storage.c | 15 +++++++-------
> kernel/bpf/cpumask.c | 2 --
> kernel/bpf/hashtab.c | 21 ++++++++-----------
> kernel/bpf/helpers.c | 4 ----
> kernel/bpf/lpm_trie.c | 24 +++++++--------------
> kernel/bpf/range_tree.c | 2 --
> kernel/bpf/syscall.c | 12 ++++++++---
> net/core/bpf_sk_storage.c | 11 ++++++----
> 12 files changed, 71 insertions(+), 88 deletions(-)
>
